This invention relates generally to surgical devices for fixation of two or more segments of tissue, and more particularly to a fixation device useful for securing two or more segments of bone in a desired spatial relation.
The use of both internal and external fixation devices to prevent major movement between two or more sections of bone is well known in the art. External casts and braces have commonly been employed to prevent movement between larger bone segments, and have been particularly useful in the fixation of long bone fractures in the extremities. For small bone segments and bones within the trunk of the body which may not be readily immobilized by braces and casts; plates, screws, nails, and wires have been implanted to maintain the relative position of these bones during the healing process. In some instances, a single screw with a uniform shaft is screwed between two bone segments to maintain these in place. Alternatively, a pinning device such as a nail may be driven into both of the bone segments to create fixation. In other applications, a lag screw is utilized with a first threaded portion passed through a first bone segment and threaded into a second segment of bone. A nut is then threaded onto a second machine threaded portion of the lag screw to reduce the fracture between the two bone fragments. Alternatively, a similar type of lag screw may be utilized in conjunction with a plate. Each of a series of lag screws is inserted into bone fragments and a plate is attached across the machine threaded portion of the lag screw. A nut is threaded onto each screw thereby attaching the plate to the bone and maintaining the spatial relationship of the bone fragments.
For smaller bones and bone fragments, small wires, commonly known as Kirschner wires (K-wires), have been inserted into the bone to immobilize the fragments. After the wires are inserted, the proximal section of the wire is cut to the desired length. While these devices have been generally successful, at least initially, in accomplishing the desired immobilization, there are a number of problems which have been encountered with their use. Specifically, it has been found that in some instances, the fixation wire can migrate from the point of its initial insertion leading to loss of fracture fixation or damage to surrounding bodily structures, such as nerves or blood vessels adjacent the entry or exit site of the wire. Moreover, cutting the wire can result in a wire end that may be sharp, leading to possible tissue irritation adjacent the wire. In an effort to limit migration of the wire, the cut end may be bent over or left protruding from the skin, also leading to possible tissue irritation and/or infection. Additionally, if the wire is trimmed too close to the bone and the wire migrates inward, the end could be lost well within the bone surface, making it impossible to retrieve without damaging the surrounding bone structure. Thus, there remains a need for an orthopedic fixation device having the beneficial affects of the above-referenced devices but offering ease of insertion, patient comfort after insertion, reduced chances for infection, and the ability to withdraw the device after a desired time period.